Recombinant adeno-associated viruses (rAAV) are vectors for in vivo gene transfer applications. Several rAAV-based gene therapies are proving to be efficacious, most notably for the treatment of Leber's congenital amaurosis, hemophilia associated with factor IX deficiency and lipoprotein lipase deficiency (Simonelli et al 2010; Nathwani et al 2011; Gaudet et al. 2010). Recently, the first rAAV-based gene therapy, Glybera, was approved by the European Medicines Agency for the treatment of lipoprotein lipase deficiency. rAAVs have also shown success in preclinical models of a large variety of diseases, including Rett syndrome, congenital ALS, Parkinson's, Huntington's disease, Spinal Muscular Atrophy, among others and for the prophylactic delivery of broad neutralizing antibodies against infectious diseases such as HIV and influenza (Garg et al 2013; Valori et al. 2010; Foust et al. 2010; Foust et al 2013; Southwell et al 2009; Balazs et al 2011; and Balazs et al 2013). In addition, rAAVs are also popular vectors for in vivo delivery of transgenes for non-therapeutic scientific studies, such as optogenics.